The present invention relates to a multi-layered slide bearing comprising a steel plate optionally plated with Cu on which a copper-lead-system bearing alloy layer and a lead alloy overlay containing Zn are formed and, more particularly, to a multi-layered slide bearing material including a copper-zinc alloy layer which is interposed between a copper-lead-system or lead-bronze-system bearing alloy layer and a lead alloy overlay containing Zn, and to a method of manufacturing the same.
A slide bearing comprising a steel plate as a backing metal plate on which a copper-lead-system or lead-bronze-system bearing alloy layer is formed has been used as a bearing for high-load application, for example, in an internal combustion engine. Although a slide bearing of this type has an excellent load carrying capacity, it involves problems in other properties required for bearing alloy such as an anti-seizure property, embeddability and conformability. Conventionally, therefore, a lead-tin-system or lead-tin-indium-system overlay has been formed on the surface of a bearing alloy layer so as to improve the anti-seizure property, embeddability and conformability.
JP-B2-54-23667 discloses a method of manufacturing such a multi-layered slide bearing. According to the method, a bimetal plate, which is formed by providing a backing metal plate with a lining of copper-lead-system or lead-bronze-system bearing alloy, and a lead alloy plate, which contains one or more of Sn, Sb, Cu, Zn, Te, In, As, Tl and other additive elements whose amount or total amount is 40% at maximum, and balance of Pb, are prepared. Next, the bimetal plate and the lead alloy plate for an overlay are rolled to bond under a temperature of from a room temperature to 200.degree. C. so that the accumulative reduction is 8 to 40%.
JP-A-61-186499 discloses a method of improving heat resistance of an overlay to enhance the wear resistance at high temperature and to improve the corrosion resistance with respect to lubricating oil whose oxidization is promoted at high temperature. In the method, an overlay is formed on the conventional bearing alloy layer, and the overlay is made of alloy containing 0.5 to 10% Zn, at least one element selected from the group consisting of 0.5 to 25% Sn, 0.1 to 5% Cu, 0.1 to 5% Sb, 0.1 to 5% As and 0.1 to 10% In, and balance of Pb and impurities.
In the above-described multi-layered slide bearing, Sn and In in the overlay improve the wear resistance and the corrosion resistance. However, when the copper-lead-system or lead-bronze-system bearing alloy layer and the overlay are brought into direct contact with each other, Sn and In in the overlay diffuse into the bearing alloy layer. As a result, amounts of Sn and In in the overlay are decreased, thereby deteriorating the wear resistance and the corrosion resistance. Consequently, as described in JP-A-61-186499, the surface of a copper-lead-system or lead-bronze-system bearing alloy layer is normally plated with Ni, and thereafter formed with an overlay. With this nickel plating layer, Sn and In in the overlay can be prevented from diffusing into the bearing alloy layer.
However, in the case of the multi-layered slide bearing with the nickel plating layer interposed between the bearing alloy layer and the overlay, the nickel plating layer will be exposed when the overlay wears and its thickness decreases. Problems will arise that hard Ni damages the mating shaft, and that corrosion resistance of the bearing alloy layer is degraded due to wear of the nickel plating layer.